I've heard the term "commando" camping, too. It means hiking without a permit, or camping in a site that is not designated specifically for camping. You might get in trouble if an authority noticed the campsite.
I've done this in Yosemite once in a while -- either sleeping in the car in a parking lot which I believe is forbidden, or throwing my bed down in the woods after dark and getting up early, and especially: leaving NO trace.
